Hello, in the May season I finished top 10 on EU using exclusively this deck, and was top 10 on NA all day until the last half an hour when I decided to try for number one but unfortunately lost a game.
With this deck you want to be controlling the board as much as you can whilst making your board difficult to remove to maximise your 4 mana buff cards (keeper, argus, kings).
This deck should use it's hero power very often and try to maintain board control, being ahead by just a 1/1 can be very threatening because of abusive and the 4 mana buff cards.
Unlike nerubian egg, with dragon egg you want to keep it alive and buff it so it can spawn multiple 2/1s. E.g. You have an abusive in hand, and a dragon egg on board vs a board of a 1/1 and a 3/2. It is generally a better play to buff the dragon egg and trade into the 1/1 rather than the 3/2.
Why do you run only 3 secrets but 2 mysterious challengers?
Generally the secrets are not that good early game with a few exceptions. By only running 3 secrets you are less likely to draw them before you play mysterious challenger. By running 2 challengers you are more likely to have a challenger on t6. Yes, you get the odd game where you draw all your secrets before challenger but it is rare. If you've already played one challenger the second one is almost a boulderfist ogre, which is fine in the late game!
Why no 2 drops?
There aren't many good 2 drops currently, and the best one (flame juggler) tends to matchup poorly vs most non-zoo decks (totem golem, fiery war axe/fierce monkey, 3/3s from rogue). Often you will need a weapon to finish off these minions, and a 1/1 from your hero power tends to do the same thing as a 2/3.
Why steward with only abusive and hero power as activators?
Steward can give your board stickiness. It also has synergy with dragon egg, causing it to spawn 2/1 divine shield minions, and with noble sacrifice + rallying blade. A 1/1 divine shield on it's own is a threat in this deck. Playing her alongside an abusive sergeant is fine on it's own.